3.3V of Portenta H7 only 3,0V

fhieber · May 4, 2023, 7:45am

Hi there,

I've been tinkering a bit with the Portenta H7 and I noticed that the 3.3V Pins of this microcontroller as well as the 3.3V pins of the Portenta Breakout board only provide 3.0V when it's powered via USB. I haven't tested the other powering options yet, but I'm curious why that is so. I could confirm the same issue on another Portenta H7. For my application, this is no problem at the moment, but if you want to use the ADCs and you're assuming that the reference voltage is 3.3V you might end up damaging the ADC when you're not using the additional AREF pin for the reference voltage.
I never experienced this with other microcontrollers so far that used 3.3V logic.

Thanks in advance for your answer.

Hm_pro · May 11, 2023, 2:06pm

Hi @fhieber

Yes that's ok, the measured 3V is due to the particular voltage that the wifi chip is supposed to run.
Regarding the use of ADCs, please visit the following article on the Help center which provides further clarification on the ADC reference voltage levels on Portenta H7.
About ADC reference voltage on Portenta H7

glassesseth · December 16, 2025, 1:46pm

The schematic states that the default is 3.3V but the line can be set anywhere from 1.1V to 3.3V. Is there any way to change the output of the PMIC? I am trying to connect to a device that requires a voltage over 3V and the 2.98V level on my 3.3V rail is causing reliability issues.

ptillisch · December 25, 2025, 6:38pm

Hi @glassesseth. Arduino provides the "Arduino_PF1550" library for use in controlling the PF1550 PMIC on the Portenta H7 board:

You can install the library via the Arduino IDE Library Manager. After installing it, you will find examples that demonstrate its usage under Arduino IDE's File > Examples > Arduino_PF1550 menu.

There isn't formal documentation for the library beyond the examples. You can use the library's source code as a reference. An overview of the library's API can be seen in the PF1550.h header file:

github.com/arduino-libraries/Arduino_PF1550

src/PF1550.h

0.3.1


      
          class PF1550
          {
          public:
          
            PF1550(PF1550_IO & io);
          
            int begin();
          
            void debug(Stream& stream);
          
            void setPMICbit(Register const reg_addr, uint8_t const posBit);
            void writePMICreg(Register const reg_addr, uint8_t const val);
            uint8_t readPMICreg(Register const reg_addr);
          
            void configLDO1(Ldo1Voltage const ldo_1_volt, bool const enable, bool const enable_in_standby, bool const enable_in_sleep);
            void configLDO2(Ldo2Voltage const ldo_2_volt, bool const enable, bool const enable_in_standby, bool const enable_in_sleep);
            void configLDO3(Ldo3Voltage const ldo_3_volt, bool const enable, bool const enable_in_standby, bool const enable_in_sleep);
          
            void configSw1(Sw1Voltage      const sw1_volt,
                           Sw1Voltage      const sw1_volt_standby,

This file has been truncated. show original

The custom enumerated types defined in PF1550/PF1550_Types.h (which are utilized in the library's API) will also likely be of interest:

github.com/arduino-libraries/Arduino_PF1550

src/PF1550/PF1550_Types.h

0.3.1


      
          enum class Ldo1Voltage : uint8_t
          {
            V_0_75 = 0x00,
            V_0_80 = 0x01,
            V_0_85 = 0x02,
            V_0_90 = 0x03,
            V_0_95 = 0x04,
            V_1_00 = 0x05,
            V_1_05 = 0x06,
            V_1_10 = 0x07,
            V_1_15 = 0x08,
            V_1_20 = 0x09,
            V_1_25 = 0x0A,
            V_1_30 = 0x0B,
            V_1_35 = 0x0C,
            V_1_40 = 0x0D,
            V_1_45 = 0x0E,
            V_1_50 = 0x0F,
            V_1_80 = 0x10,
            V_1_90 = 0x11,

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3.3V of Portenta H7 only 3,0V

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